Highly Stable Quantum Dot-Containing Polymer Films

ABSTRACT

Highly stable films containing semiconductor nanoparticles (“quantum dots”) are prepared from resins containing a fast-curing inner phase having a high glass transition temperature (T g ) and certain inner phase/outer phase combinations. The resins may comprise an inner phase and outer phase (but may appear to be a single phase due to their homogeneous appearance when viewed using an optical microscope). The method provides a highly scalable and cost-effective procedure for preparing films that are resistant to light, elevated temperatures, moisture, and oxygen.

CROSS-REFERENCE TO RELATED APPLICATIONS:

This application claims the benefit of U.S. Provisional Application No.62/294,783, filed on Feb. 12, 2016, which is hereby incorporated byreference in its entirety.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

Not Applicable

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention generally relates to semiconductor nanoparticles(“quantum dots”). More particularly, it relates to polymer filmsincorporating heavy metal-free quantum dots.

2. Description of the Related Art including information disclosed under37 CFR 1.97 and 1.98

Multi-phase and two-phase polymer films containing heavy metal-freesemiconductor nanoparticles dispersed in an inner phase which is thendispersed in a suitable gas barrier outer phase have been describedpreviously—see, e.g., U.S. Pub. No. 2015/0047765 “Quantum dot filmsutilizing multi-phase resin” and U.S. Pub. No. 2015/0275078 “Quantum dotcompositions.”

However, there have been many challenges in obtaining truly stable filmsespecially under testing conditions that include a dark test (0/60/RH)[0 mW/cm² irradiance/at 60° C./RH=room humidity (not measured)] inaddition to a light test (106/60/90) [90% relative humidity]. The darktest is especially challenging for currently available red-emittingquantum dots (QDs) utilized in conjunction with barrier films having awater vapor transmission rate (WVTR) on the order of 10⁻² g/m² day(e.g., i-Components TBF1004 barrier film, i-Components Co. Ltd., 701,Family Tower, 958-2, Youngtong-dong, Paldal-gu Soowon-si, Gyeonggi-do,Korea) having a resin film thickness of 50 microns or less.

BRIEF SUMMARY OF THE INVENTION

This invention concerns the preparation of highly stable films fromresins containing a fast-curing inner phase preferably having a highglass transition temperature (T_(g)) (preferably greater than 35° C. andmore preferably greater than 80° C.) and certain inner phase/outer phaseresin combinations. The resins described consist of an inner phase andouter phase but in some cases may be referred to as a single phase dueto their homogeneous appearance when viewed using an optical microscope.The method of the invention provides a highly scalable andcost-effective way of preparing stable films.

Herein, stability test conditions are reported as “(x/y/z)” where x isthe irradiance in mW/cm²; y is the temperature in ° C.; and z is therelative humidity in percent.

The following abbreviations, acronyms, and trade names are usedthroughout this disclosure:

-   IPM isopropyl myristate-   YR011 acrylate functionalized silica nanoparticle resin from Showa    Denko K.K. (Shiba Daimon, Minato-ku Tokyo JAPAN)-   AEROSIL® R106 fumed silica (EVONIK DEGUSSA GMBH Rellinghauser    Strasse 1-11 45128 Essen FED REP GERMANY)-   CN104 bisphenol A epoxy diacrylate oligomer from Sartomer (Sartomer    Technology USA, LLC Suite 202, 103 Foulk Rd., Wilmington Del. 19803)-   CN104680 bisphenol A epoxy diacrylate blend from Sartomer-   CN104C80 80/20 blend of CN104 and 2-hydroxyethyl acrylate (HEA)-   CN104E70C5 70/20/5 blend of CN104, 2-hydroxymethyl methacrylate    (HEMA) and 2-hydroxyethyl acrylate (HEA)-   CN146 monofunctional adhesion-promoting acrylic oligomer from    Sartomer-   SR833S tricyclodecane dimethanol diacrylate (a low-viscosity    bifunctional acrylate monomer that can be polymerized by free    radicals)-   LMA lauryl methacrylate-   TMPTMA trimethylolpropane trimethacrylate-   IRG651 IRGACURE® 651 (2,2-dimethoxy-1,2-diphenylethan-1-one)    photo-initiator from BASF (BASF SE Carl-Bosch-Strasse 38    Ludwigshafen GERMANY)-   IRG819 IRGACURE® 819    (bis(2,4,6-trimethylbenzoyl)-phenylphosphineoxide) photo-initiator    from BASF-   IBOA isobornyl acrylate-   YR301 another acrylate-functionalized silica nanoparticle resin from    Showa Denko K.K.-   TMPTA trimethylolpropane triacrylate-   CITHROL DPHS PEG 30 dipolyhydroxystearate surfactant (Croda    International Plc, Snaith, Goole, East Yorkshire DN14 9AA UK)-   IPM isopropyl myristate-   TCDMDA tricyclodecane dimethanol diacrylate-   LA lauryl acrylate-   HEA 2-hydroxyethyl acrylate-   HEMA 2-hydroxyethyl methacrylate-   4-hydroxy-TEMPO free-radical inhibitor    (4-Hydroxy-2,2,6,6-tetramethylpiperidine 1-oxyl, or “TEMPOL”)

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING(S)

FIG. 1 is a graph showing the results of a light stability test for filmprepared from 281C resin (IBOA/(YR011/0.36 wt. % IRG819)).

FIG. 2 is a graph showing the results of a light stability test for filmprepared from 282B resin (IBOA/(YR301/1 wt. % IRG819)).

FIG. 3 is a graph showing the results of a dark stability test (0/60/90)for film prepared from 281A resin (LMA/TMPTMA/(YR011/0.36 wt. %IRG819)).

FIG. 4 is a graph showing the results of a dark stability test (0/60/90)for film prepared from 281C resin (IBOA/(YR011/0.36 wt. % IRG819)).

FIG. 5 is a graph showing the results of a light stability test(106/60/90) for film prepared (298B) from IBOA/CN104C80 resin.

FIG. 6 is a graph showing the results of a dark stability test (0/60/90)for film prepared (298B) from IBOA/CN104C80 resin.

FIG. 7 is a graph showing the results of a dark stability test (0/60/RH)for film prepared (383C) from (IBOA/TMPTA)/CN104E70C5.

FIG. 8 is a graph showing the results of a light stability test(106/60/90) for film prepared (383C) from (IBOA/TMPTA)/CN104E70C5.

FIG. 9 is a graph showing the results of a dark stability test (0/60/RH)for film prepared (3831) from IBOANR301.

FIG. 10 is a graph showing the results of a dark stability test(0/60/RH) for film prepared (383J) from (IBOA/Cithrol)NR301.

FIG. 11 is a graph showing the results of a dark stability test(0/60/RH) for film prepared (383K) from (IBOA/TMPTA)/YR301.

FIG. 12 is a graph showing the results of a light stability test(106/60/90) for film prepared (3831) from IBOANR301.

FIG. 13 is a graph showing the results of a light stability test(106/60/90) for film prepared (383J) from (IBOA/Cithrol)NR301.

FIG. 14 is a graph showing the results of a dark stability test(0/60/RH) for film prepared (383E) from IBOA/SR833S.

FIG. 15 is a graph showing the results of a dark stability test(0/60/RH) for film prepared (383F) from ((IBOA/Cithrol)/SR833S).

FIG. 16 is a graph showing the results of a dark stability test(0/60/RH) for film prepared (383G) from ((IBOA/TMPTA)/SR833S).

FIG. 17 is a graph showing the results of a light stability test(106/60/90) for film prepared (383F) from (IBOA/Cithrol)/SR833S.

FIG. 18 is a graph showing the results of a light stability test(106/60/90) for film prepared (383G) from (IBOA/TMPTA)/SR833S.

DETAILED DESCRIPTION OF THE INVENTION

From a series of experiments it was discovered that, the higher thephase separation between the inner and outer phases, the better the gasbarrier properties of the barrier resin are maintained. For example,IPM/Aerosil R106 inner phases showed good back light unit (BLU)stability (2.5 mW/cm²) when used with a bisphenol A epoxy diacrylateouter phase (CN104B80 from Sartomer) but very poor stability withsignificant edge ingress of oxygen and/or moisture in cuts from thebarrier film laminated sample when used with YR011 (acrylatefunctionalized silica nanoparticle resin from Showa Denko K.K.) or a50:50 wt. % acrylic oligomer (CN146 from Sartomer)/tricyclodecanedimethanol diacrylate (TCDMDA or SR833S from Sartomer) outer phase. Thepolarity of the CN104B80 in this application is important to providegood phase separation and less contamination of the outer phase withuncured liquid. However, this limits the scope of this inner phase informulations and the interaction between inner and outer phase willlikely increase as efforts to increase emulsion stability of theseresins are made. A higher viscosity of the inner phase or outer phasemay be important in reducing the diffusion of the inner phase into theouter phase as evidenced by the greater edge ingress in the barrier filmlaminated sample observed in films from IPM-only/YR011 resin (233A) ascompared to the higher viscosity (IPM/Aerosil R106)/YR011 resin (233B).

When a cured inner phase of lauryl methacrylate/trimethylolpropanetrimethacrylate (LMA/TMPTMA) was used, more stable films were obtainedfor YR011 and for 50:50 wt. % CN146/SR833S blend despite the fact thatgreater diffusion of the more polar inner phase (as compared to IPM)into the outer phase might be expected in these systems.

Experiments using the same outer phases with heavy metal-freesemiconductor nanoparticle beads to prepare resins exhibited betterstability than cured inner phase resin. The beads were prepared fromLMA/TMPTMA but contained a higher proportion of TMPTMA cross-linker andwere fully cured before mixing with the outer phase. It was concludedthat full curing of the inner phase is necessary in these systems inorder to minimize the reduction of gas barrier properties due to themixing of soft, uncured, inner phase into the outer phase. Because ofthe time-scale of polymerization of the two-phase resins (30 secondsunder mercury lamps), an acrylate as opposed to a methacrylate innerphase may provide a more suitable curing system.

Experiments using isobornyl acrylate (IBOA) and IBOA/lauryl acrylate(LA) as an inner phase were carried out with YR011, YR301 and CN104C80(CN104: 2-hydroxyethyl acrylate (HEA)=80:20 wt. %) as the outer phase.IBOA was chosen because of its high T_(g) (94° C. per Sigma Aldrich) andwould result in a lesser amount of soft material in the outer phase thanLA. A combination of LA and IBOA was used to provide more flexibility inthe film which may be needed in a roll-to-roll process. LA also offersslightly better compatibility with heavy metal-free semiconductornanoparticles than IBOA. A summary of some of the experiments carriedout and results obtained are presented in TABLE 1 and TABLE 2. PLQYmeasurements were made using a Hamamatsu instrument and EQE values wereobtained using a LABSPHERE® integrating sphere (LABSPHERE INC. 231Shaker Street NORTH SUTTON NEW HAMPSHIRE 03260).

Examples of acrylate monomers having relatively high glass transitiontemperatures (T_(g)) or melting temperatures (T_(m)) include: BehenylAcrylate (BEA, T_(g)=54° C.); tent-Butyl Acrylate (TBA, T_(g)=43-107°C.); Dihydrodicyclopentadienyl Acrylate (DCPA, T_(g)=110° C.); andStearyl Acrylate (SA, T_(m)=41-49° C.).

Examples of methacrylate monomers having relatively high glasstransition temperatures (T_(g)) or melting temperatures (T_(m)) include:Behenyl Methacrylate (BEMA, T_(m)=44° C.); tert-Butyl Methacrylate(TBMA, T_(g)=117° C.); Cyclohexyl Methacrylate (CHMA, T_(g)=105° C.);and Methyl methacrylate (MMA, T_(g)=105° C.).

TABLE 1 Resins prepared for comparing acrylate and methacrylate innerphases with YR011-, YR301-, and CN104-based outer phases. Exp Innerphase (20 wt. %) Outer phase (80 wt. %) Quantum dots mg/g 281ALMA/TMPTMA (9:1 mol) and YR011 and IRG819 (0.36 wt. % Green 10.2IRG819/651 (13.5 mg and 4.5 mg/10 mmol) initiator) - no inhibitor 414₋blend (PL = 523 nm) 281B LA/IBOA (67 wt. % LA) and IRG819 YR011 andIRG819 (0.36 wt. % Green 440 13.3 (0.5 wt. %) initiator) - no inhibitor(PL = 523 nm) 281C IBOA and IRG819 (0.5 wt. %) YR011 and IRG819 (0.36wt. Green 440 13.3 %) - no inhibitor (PL = 523 nm) 282A IBOA and IRG819(0.5 wt. %) YR011 and IRG819 (0.36 wt. Green 440 13.3 %) - no inhibitor(PL = 523 nm) 282B IBOA and IRG819 (0.5 wt. %) YR301 and IRG819 (1 wt.%) - Green 440 13.3 no inhibitor (PL = 523 nm) 298A and B IBOA andIRG819 (0.5 wt. %) CN104C80 and IRG819 (1 wt. Green 421 7.58 green/ (A =15 s curing %) - with inhibitor and red 098 0.621 red B = 30 s curing)Note: samples 281C and 282A are the same.

TABLE 2 Optical properties of films prepared from the resins listed inTABLE 1. Films were ca.100-μm thick and were coated between i-Component125-μm barrier films. Curing was carried out under mercury lamps for 30seconds except for 298A which was carried out for 15 seconds. DAY 0 DAY1 DAY 6 PLQY EQE/Abs EQE/Abs EQE/Abs PL Exp (%) (%) (%) (%) Ingress (mm)(nm) 281A 52 45/23 43/25 40/24 ~1 544 281B 60 52/31 51/32 49/32 ~0.6 541281C 60 55/32 53/34 52/34 ~0.3 541 282A 60 53/32 53/33 52/32 ~0.3 542282B 54 48/33 49/34 48/34 <0.1 543 298A 48 44/29 — — — — 298B 48 43/29 —— — — (samples 281C and 282A illustrate sample-to-sample variation)

For YR011 outer phase with 0.36 wt. % IRG819, it was found that anIBOA-only inner phase gave the least edge ingress due to moisture and/oroxygen degradation observed in the barrier film laminated samples on aBLU. It was previously found that increasing the concentration of IRG819in YR011 to 1 wt. % significantly increased the stability of(LMA/TMPTMA)NR011 resins. It is contemplated that the main reason forthis is that the curing of diffused LMA/TMPTMA into the outer phase issignificantly increased at this higher initiator concentration. A new,less-expensive, acrylate-functionalized, silica nanoparticle resin(YR301) was also tested with an IBOA inner phase in 282B at the higherphotoinitiator concentration. The edge ingress on this sample wassignificantly less than for other samples. It is noted that theIBOA/(YR301 or YR011) showed significantly better emulsion stabilitythan LMA/TMPTMA indicating that the more polar IBOA was diffusing andinteracting more with the outer phase. The increased stability of theIBOA samples compared to LA or LMA based inner phases implies that theuse of a fast-curing, high-T_(g) inner phase may be critical inmaintaining gas barrier properties. In general, acrylates are preferredover methacrylates due to their higher propagation rate constants forthe radical polymerization reactions that may be utilized.

All the above samples with acrylate-functionalized silica nanoparticleresins did not show adequate stability on the light test (106/60/90).Although, edge ingress in the barrier film laminated sample wasvirtually zero after 120 hours for IBOA/YR301 with 1 wt. % IRG819(282B), the drop in stability was more pronounced than 281C. The higherinitiator concentration in 282B may have caused bleaching of the filmduring the light test. FIG. 1 and FIG. 2 show the difference instability. It is contemplated that the mixing of the inner phase and theouter phase in 282B was possibly not efficient (incomplete phaseseparation was observed by optical microscopy of a film prepared from282B resin) and was likely the cause of the observed drop in stability(see explanation infra).

Two of these samples were subjected to a dark test at 90% humidity(0/60/90) and the difference in stability between LMA/TMPTMA and IBOAinner phases is shown in FIGS. 3 and 4 (different quantum dots used).

For the CN104C80 outer phase (298), there was no difference observedbetween curing for 15 and 30 seconds. The results of light and darkstability test are shown in FIG. 5 and FIG. 6.

A number of outer and inner phases were tested. The examples includethree outer phases and three inner phases as they best illustrate thestability of the systems. Red-emitting quantum dots at a concentrationof 2.40 mg/g were used to prepare films between i-Components Co. 50-μmbarrier films at a thickness of 50 μm.

Outer Phase Examples:

1. CN104E70C5 outer phase (69.3 wt. % CN104; 24.75 wt. % 2-hydroxyethylmethacrylate (HEMA); 4.95 wt. % 2-hydroxyethyl acrylate (HEA); 125 ppm4-Hydroxy-TEMPO inhibitor; 1 wt. % IRG 819).

2. YR301 outer phase (99.0 wt. % YR301; 1.0 wt. % IRG819; 125 ppm4-Hydroxy-TEMPO inhibitor).

3. SR833S outer phase (99.0 wt. % SR833S; 1.0 wt. % IRG819; 125 ppm4-hydroxy-TEMPO inhibitor).

Inner Phase Preparation and Mixing with Above Outer Phase Examples:

1. Red-emitting, heavy metal-free, semiconductor nanoparticles (PL=633nm, FWHM=57 nm, QY=78%) in toluene were dried under high vacuum andre-dispersed in IBOA at a concentration of 23.8 mg/g by stirringovernight. The concentrated quantum dot solution was further dilutedwith IBOA and IRG819 was added at a concentration of 0.3 wt. % toprovide a final concentration of 11.9 mg/g. This inner phase (20 wt. %)was mixed at 500 rpm with outer phase for 10 minutes to provide ared-emitting quantum dot concentration of 2.4 mg/g.

2. Red-emitting, heavy metal-free, semiconductor nanoparticles intoluene were dried under high vacuum and redispersed in IBOA at aconcentration of 23.8 mg/g by stirring overnight. The concentratedquantum dot solution was further diluted with IBOA and mixed withCithrol DPHS (final concentration of 2.5 wt. % in inner phase) at 40° C.for 1 hr. After cooling, IRG819 was added at concentration of 0.3 wt. %to provide a final concentration of 11.9 mg/g. This inner phase (20 wt.%) was mixed at 500 rpm with outer phase for 10 minutes to provide ared-emitting quantum dot concentration of 2.4 mg/g.

3. Red-emitting, heavy metal-free, semiconductor nanoparticles intoluene were dried under high vacuum and redispersed in IBOA at aconcentration of 23.8 mg/g by stirring overnight. The concentratedquantum dot solution was further diluted with IBOA and TMPTA (5 wt. % ofinner phase) and IRG819 was added at concentration of 0.3 wt. % toprovide a final concentration of 11.9 mg/g. This inner phase (20 wt. %)was mixed at 500 rpm for 10 minutes with outer phase to provide ared-emitting quantum dot concentration of 2.4 mg/g.

CN104E70C5-based Resins (Blend of Bisphenol A Epoxy Diacrylate Oligomer,2-hydroxymethyl Methacrylate and 2-hydroxyethyl Acrylate)

The resins prepared are listed in TABLE 3.

TABLE 3 Resins prepared from CN104E70C5 and IBOA-based inner phases (IP)and optical properties of films. Films were prepared at day 0, day 5 andday 14 from the same resin after remixing. Day 0 and Day 14 films werephoto- brightened (PB) by exposure on a backlight unit for 16 hours. RedInner Phase QY at 450 nm LED Abs PL/FWHM Luminous Flux Film Code (20%)(%) EQE (%) (%) (nm) CIEx CIEy (lumens) 383A Day 0 IBOA 59 34.0 18655/58 0.18 0.036 147 383A Day 5 IBOA 52 30.7 17 656/58 383A Day 14 IBOA52 35.1 19 655/59 383A Day 0 (PB) IBOA 58 36.1 18 655/57 383A Day 14(PB) IBOA 59 37.7 19 654/57 383B Day 0 IBOA/2.5% 61 36.5 16 654/57 0.180.036 156 CITHROL 383B Day 5 IBOA/2.5% 55 29.3 14 653/57 0.175 0.033 152CITHROL 383B Day 14 IBOA/2.5% 46 25.5 12 655/57 CITHROL 383B Day 0 (PB)IBOA/2.5% 59 38.3 16 653/56 CITHROL 383B Day 14 (PB) IBOA/2.5% 54 28.111 653/56 CITHROL 383C Day 0 IBOA/5 MOL % 58 34.0 18 655/58 0.018 0.036148 TMPTA 383C Day 5 IBOA/5 MOL % 54 32.5 18 655/58 0.179 0.035 143TMPTA 383C Day 14 IBOA/5 MOL % 53 34.9 19 655/58 TMPTA 383C Day 0 (PB)IBOA/5 MOL % 57 36.5 17 656/57 TMPTA 383C Day 14 (PB) IBOA/5 MOL % 5937.1 19 656/57 TMPTA

The pot life of the resins (except sample B) was good, and clear filmswere obtained upon coating. A minimal decrease in red shift was observedwhen Cithrol was used suggesting that Cithrol only marginally improvesthe dispersion of quantum dots in IBOA. The microscope images for thefilms all displayed clear inner domains dispersed in outer phase.

All the samples exhibited poor dark stability (0/60/RH) and the samplewith TMPTA (383C) had slightly longer lifetime for light stability(106/60/90). It is clear that this CN104-based resin (as is the casewith standard CN104/IPM-based resins) is less stable for semiconductornanoparticles in the dark test. It is contemplated that the highpolarity of its components (e.g. HEMA) allows water to permeate into thefilm. Modifying the outer phase with less water soluble components mayimprove stability. FIGS. 7 and 8 illustrate the stability of 383C.

YR301-based Resins (Acrylate-functionalized Silica Nanoparticle Resin)

The resins prepared are listed in TABLE 4.

TABLE 4 Resins prepared from YR301 and IBOA-based inner phases andoptical properties of films. Films were prepared at day 0, day 5 and day14 from the same resin after remixing. Day 0 and Day 14 films werephoto-brightened (PB). QY at Red Luminous Inner Phase Outer Phase 450 nmLED Abs PL/FWHM Flux Film Code (IP) (OP) (%) EQE (%) (%) (nm) CIEx CIEy(lumens) 383I Day 0 IBOA YR301 60 35.9 21 653/58 0.188 0.04 150 383I Day5 IBOA YR301 56 33.4 22 656/60 0.187 0.039 145 383I Day 14 IBOA YR301 5437.3 22 656/60 383I Day 0 (PB) IBOA YR301 58 38.9 20 655/57 383I Day 14(PB) IBOA YR301 57 40.1 22 655/59 383J Day 0 IBOA/2.5% YR301 61 36.2 17653/57 0.19 0.041 161 CITHROL 383J Day 5 IBOA/2.5% YR301 57 33.7 17652/58 CITHROL 383J Day 14 IBOA/2.5% YR301 57 37.5 20 652/58 CITHROL383J Day 0 (PB) IBOA/2.5% YR301 55 36.6 17 650/57 CITHROL 383J Day 14(PB) IBOA/2.5% YR301 55 38.2 20 651/57 CITHROL 383K Day 0 IBOA/5 MOL %YR301 60 36.0 21 654/57 0.189 0.04 151 TMPTA 383K Day 5 IBOA/5 MOL %YR301 55 36 20 655/59 TMPTA 383K Day 14 IBOA/5 MOL % YR301 54 37.3 22655/59 TMPTA 383K Day 0 (PB) IBOA/5 MOL % YR301 58 37.1 21 654/58 TMPTA383K Day 14 IBOA/5 MOL % YR301 58 40.4 22 655/59 (PB) TMPTA

The pot life of the resins was good and clear films were obtained oncoating. The absorbance was slightly higher for YR301 than CN104E70C5.In microscope images, clear inner domains could be seen except for thesample containing Cithrol DPHS where the phase separation was no longerclear.

Stability plots are presented in FIGS. 9-13. For the dark stabilitytests, excellent stability was observed for the IBOA-only inner phaseespecially during the first 500 hours with the QD peak plot closelymatching the LED peak intensity plot. The addition of Cithrol DPHS has anegative effect with a greater deviation between the two lines in theearly stages. This is expected inasmuch as the addition of a waxynon-curing material would result in softening of the outer phase. Theaddition of TMPTA also causes a slightly bigger deviation possiblybecause of the diffusion of polar TMPTA into the outer phase.

For the light stability plots, samples 3831 and 383J were stable after500 hours but the Cithrol-containing sample remained more stable past500 hrs. The mixing in 383I is believed to be better than in 282B (theonly differences being green quantum dots were used and the final resinwas less fluid after mixing) giving clear phase separation between theinner and outer phases. This may result in a better gas barrier resinand better protection of the inner phase from the high initiatorconcentration in the outer phase hence providing much better initialstability.

In general, the use of YR301 with a fast-curing, high-T_(g) inner phaseis preferred in terms of dark stability.

SR833S-based Resins (Tricyclodecane Dimethanol Diacrylate Resin)

The resins prepared are listed in TABLE 5.

TABLE 5 Resins prepared from SR833S and IBOA-based inner phases andoptical properties of films. Films were prepared at day 0, day 5 and day14 from the same resin after remixing. Day 0 and day 14 films werephoto-brightened (PB). QY at Red Luminous Inner Phase Outer Phase 450 nmLED Abs PL/FWHM Flux Film Code (IP) (OP) (%) EQE (%) (%) (nm) CIEx CIEy(lumens) 383E Day 0 IBOA SR833S 53 30.3 17 655/58 0.178 0.035 148 383EDay 5 IBOA SR833S 52 30.4 16 654/58 0.179 0.035 146 383E Day 14 IBOASR833S 53 34.2 17 655/58 383E Day 0 (PB) IBOA SR833S 53 33.2 17 653/58383E Day 14 (PB) IBOA SR833S 57 35.6 17 655/58 383F Day 0 IBOA/2.5%SR833S 60 33.2 15 645/59 0.184 0.039 179 CITHROL 383F Day 5 IBOA/2.5%SR833S 56 31.4 15 645/61 0.185 0.04 180 CITHROL 383F Day 14 IBOA/2.5%SR833S 57 35 15 642/61 CITHROL 383F Day 0 (PB) IBOA/2.5% SR833S 55 30.815 645/61 CITHROL 383F Day 14 (PB) IBOA/2.5% SR833S 57 33.5 15 645/61CITHROL 383G Day 0 IBOA/5 MOL % SR833S 56 32.3 16 655/57 0.181 0.036 147TMPTA 383G Day 5 IBOA/5 MOL % SR833S 53 30.8 16 654/59 TMPTA 383G Day 14IBOA/5 MOL % SR833S 51 33.7 19 656/58 TMPTA 383G Day 0 (PB) IBOA/5 MOL %SR833S 54 32.8 16 654/58 TMPTA 383G Day 14 (PB) IBOA/5 MOL % SR833S 5737.2 19 655/58 TMPTA

The pot life of the resins was good, and clear films were obtained uponcoating. In microscope images, inner domains could be seen (less clearlythan for CN104E70C5 and YR301) except for the sample containing CithrolDPHS where the phase separation was no longer clear. Unlike the case forCN104E70C5 and YR301, the red shift was observed to be significantlyless with the use of Cithrol.

Stability plots are presented in FIGS. 14-18. The SR833S-based films areless stable than YR301-based films on dark test. Similarly, the additionof Cithrol DPHS had a slight negative effect with a bigger deviationbetween the QD and peak intensity lines. However, in comparison to mostsystems available, these samples remained relatively stable as seen bythe leveling of the peak intensity over time.

For the light stability plots, samples 383F and 383G were stable after500 hours with the sample containing Cithrol DPHS showing betterstability especially after 1000 hrs. In this resin, where the innerphase and outer phase are closer in polarity, Cithrol may help protectthe quantum dots from the high concentration of initiator in the outerphase.

A fast-curing, high-T_(g) inner phase improves the stability oftwo-phase resins. Such films exhibit good dark-test stability likely dueto the reduction of uncured soft material in the outer phase. Lightstability was observed to be good when there was good phase separationbetween the inner and outer phases (e.g. IBOA/YR301). An additive suchas Cithrol may be beneficial when the inner and outer phases are closerto one another in polarity (e.g. IBOA/SR833S).

Advantages of the invention include:

1. The above-described resin systems are commercially scalable.

2. These resins exhibit very good stability (under both light and darkconditions) for 50-micron red-emitting-QD films between i-Components Co.barrier film.

3. Emulsion stability and pot life of the resins are good.

The foregoing presents particular embodiments of a system embodying theprinciples of the invention. Those skilled in the art will be able todevise alternatives and variations which, even if not explicitlydisclosed herein, embody those principles and are thus within the scopeof the invention. Although particular embodiments of the presentinvention have been shown and described, they are not intended to limitwhat this patent covers. One skilled in the art will understand thatvarious changes and modifications may be made without departing from thescope of the present invention as literally and equivalently covered bythe following claims.

What is claimed is:
 1. A film comprising: a plurality of semiconductor nanoparticles dispersed in an uncured inner phase that comprises isopropyl myristate; and, an outer phase that comprises a bisphenol A epoxy diacrylate oligomer.
 2. The film recited in claim 1 wherein the inner phase additionally comprises fumed silica.
 3. The film recited in claim 1 additionally comprising: an oxygen-barrier film.
 4. A film comprising: a plurality of semiconductor nanoparticles dispersed in a cured inner phase that comprises lauryl methacrylate and trimethylolpropane trimethacrylate; and, an outer phase that comprises an acrylate-functionalized silica nanoparticle resin.
 5. The film recited in claim 4 additionally comprising: an oxygen-barrier film.
 6. A film comprising: a plurality of semiconductor nanoparticles dispersed in a cured inner phase that comprises lauryl methacrylate and trimethylolpropane trimethacrylate; and, an outer phase that comprises a monofunctional adhesion-promoting acrylic oligomer and a tricyclodecane dimethanol diacrylate.
 7. The film recited in claim 6 wherein the outer phase comprises substantially equal amounts of the monofunctional adhesion-promoting acrylic oligomer and the tricyclodecane dimethanol diacrylate.
 8. The film recited in claim 6 additionally comprising: an oxygen-barrier film.
 9. The film recited in claim 6 wherein the semiconductor nanoparticles comprise red-emitting quantum dots.
 10. The film recited in claim 6 wherein the semiconductor nanoparticles comprise red-emitting quantum dots and green-emitting quantum dots.
 11. A two-phase resin system comprising: an outer phase; and an inner phase that comprises an acrylate having a plurality of semiconductor nanoparticles dispersed therein.
 12. A film comprising: a first layer comprising an oxygen barrier; a second layer, disposed on the first layer, said second layer comprising a two-phase resin system comprising an outer phase; and an inner phase that comprises an acrylate having a plurality of semiconductor nanoparticles dispersed therein.
 13. A film comprising: a plurality of semiconductor nanoparticles dispersed in an inner phase that comprises isobornyl acrylate and, optionally, a stabilizing additive; and, an outer phase that comprises a resin that provides a phase separation from the inner phase.
 14. The film recited in claim 13 wherein the outer phase comprises an acrylate-functionalized silica nanoparticle resin.
 15. The film recited in claim 13 wherein the outer phase comprises a bisphenol A epoxy diacrylate oligomer and 2-hydroxyethyl acrylate.
 16. The film recited in claim 15 wherein the outer phase comprises about 80% bisphenol A epoxy diacrylate oligomer and about 20% 2-hydroxyethyl acrylate.
 17. The film recited in claim 13 wherein the inner phase additionally comprises lauryl acrylate.
 18. The film recited in claim 13 wherein the outer phase comprises an acrylate-functionalized silica nanoparticle resin and the inner phase consists essentially of isobornyl acrylate and semiconductor nanoparticles.
 19. The film recited in claim 18 further comprising about 1% by weight of a photo-initiator.
 20. The film recited in claim 19 wherein the photo-initiator is bis(2,4,6-trimethylbenzoyl)-phenylphosphineoxide. 